You can hit every animal except of those of the same species (doesn't apply for sharks, they can eat other sharks too!)
If you are hit by someone stronger than you, you'll get 15% slower for 5 seconds.

07-21
PD:
- Fixed can't respawn if server is full
- Piranha becomes an option at seagull level
ALL:
- Fixed some animals being unable to damage others
- Manatee and piranha boosts reduced
- Sunfish temp. and pressure time increased
- Remora now has 50% of armor pen.
07-19
- Server performance improved
- Fixed: Food spawning inside ground
- Top tier won't collide with tier 1 animals (except bots)
PD
- Pearl can't be picked by tier 1 animals
- Correct scorer displayed in finish screen
07-14 BETA PUBLISHED
- Beta is now official, to gather further feedback. If any fixes are needed, a new version will be uploaded
- Beta includes a new Biome, and new animals, designed by:
Bald Eagle: John Fallot (Pathos316): Portfolio)
Hippo, Crocodile, etc.: FlllllSH (Reddit)
Snapping Turtle: TheGiantSlug (Reddit)
And many ideas given by countless players, like DogJelly and others.